Display device

ABSTRACT

A display device is provided. The display device includes an anti-reflection film. The anti-reflection film includes a base film, a retardation coating layer disposed on a first side of the base film so as to delay a phase of transmitted light, and a polarizer coating layer disposed on a second side of the base film so as to allow a polarization component of the transmitted light in a specific direction to pass through, wherein the retardation coating layer and the polarizer coating layer are formed by applying a liquid crystal on the base film.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 15/058,092 filed on Mar. 1, 2016, which is adivisional application of U.S. patent application Ser. No. 14/185,575filed on Feb. 20, 2014, now U.S. Pat. No. 9,310,638 which claimspriority to and the benefit of Korean Patent Application No.10-2013-0104911 filed in the Korean Intellectual Property Office on Sep.2, 2013, the entire contents of which are incorporated herein byreference.

BACKGROUND (a) Technical Field

The present disclosure relates to a display device, and moreparticularly, to a display device including an anti-reflection filmhaving a thin structure.

(b) Description of the Related Art

When external light is reflected or scattered on a display surface of adisplay device, the image on the display device cannot be properlyobserved. The reflection or scattering of external light is particularlycommon on portable devices (such as mobile phones, PMPs (portablemultimedia players), PDA (personal digital assistants), and laptopcomputers)) since these portable devices are often used outdoors.

Various methods have been proposed to overcome the problem of thereflection and scattering of external light on display devices. Forexample, an anti-reflection film may be attached to the display surfaceof the display device. The anti-reflection film absorbs externallyreflected and scattered light, and allows only the image displayed onthe display device to be transmitted, thereby producing a clearerdisplay image.

Recently, foldable display devices having bending and foldingcharacteristics have been developed. A foldable display device hasnumerous advantages over non-foldable display devices. For example, thefoldable display device highly portable and can be easily carriedaround. Also, a large display screen can be implemented on the foldabledisplay device. Furthermore, the foldable display device may be used invarious mobile equipment (such as mobile phones, PMPs, PDPs, navigationdevices, UMPCs (ultra-mobile PCs)), may serve as a TV or a monitor, andmay be used to read electronic books or electronic newspapers.

For an anti-reflection film to work properly, the anti-reflection filmneeds to have good adhesion to the foldable display device. However,presently developed anti-reflection films are limited to a thickness ofabout 100 um, which affects the bendability and curvature radius of thefoldable display device. For example, at this thickness (of about 100um), the anti-reflection film may delaminate from the foldable displaydevice after repeated bendings/foldings.

Accordingly, to fold the foldable display device at a smaller curvatureradius and to improve adhesion of the anti-reflection film to thefoldable display device, an anti-reflection film having a thin structuremay be required.

SUMMARY

The present disclosure is directed to address at least the abovedeficiencies relating to the adhesion of anti-reflection films infoldable display devices and the curvature radius of those foldabledisplay devices.

According to some exemplary embodiments of the inventive concept, adisplay device including an anti-reflection film is provided. Theanti-reflection film includes a base film; a retardation coating layerdisposed on a first side of the base film so as to delay a phase oftransmitted light; and a polarizer coating layer disposed on a secondside of the base film so as to allow a polarization component of thetransmitted light in a specific direction to pass through, wherein theretardation coating layer and the polarizer coating layer are formed byapplying a liquid crystal on the base film.

In some embodiments, the polarizer coating layer may be disposed on theretardation coating layer.

In some embodiments, the anti-reflection film may further include anover-coating layer disposed on the polarizer coating layer.

In some embodiments, the over-coating layer may include a UV-absorber.

In some embodiments, the over-coating layer may include particles forantiglare.

In some embodiments, the display device may further include a touchscreen panel, wherein the base film may be attached to the touch screenpanel.

In some embodiments, the retardation coating layer may delay the phaseof the transmitted light by a quarter wavelength (λ/4), and a firstdirection of an optical axis of the retardation coating layer and asecond direction of an optical axis of the polarizer coating layer mayform an angle of 45°.

In some embodiments, the optical axis of the base film may be the sameas the optical axis of the retardation coating layer.

In some embodiments, the anti-reflection film may further include asecond over-coating layer disposed between the retardation coating layerand the polarizer coating layer.

In some embodiments, the an reflection film may further include a secondover-coating layer disposed on the retardation coating layer; and asecond retardation coating layer disposed on the second over-coatinglayer, wherein the polarizer coating layer is disposed on the secondretardation coating layer.

In some embodiments, the retardation coating layer may delay the phaseof the transmitted light by a quarter wavelength (λ/4), and the secondretardation coating layer may delay the phase of the transmitted lightby a half wavelength (λ/2).

In some embodiments, an axis of a sum of vectors of a first direction ofan optical axis of the retardation coating layer and a second directionof an optical axis of the second retardation coating layer may have anangle of 45° to third direction of an optical axis of the polarizercoating layer

In some embodiments, the anti-reflection film may further include anoptical coating layer disposed on the polarizer coating layer, whereinthe optical coating layer includes at least one of a low-reflectioncoating, an anti-reflection coating, and an anti-fingerprint coating.

In some embodiments, the polarizer coating layer may be disposed on thebase film, and the retardation coating layer may be disposed beneath thebase film.

In some embodiments, the anti-reflection film may further include anover-coating layer disposed on the polarizer coating layer; and aninsulating coating layer disposed beneath the retardation coating layer.

In some embodiments, the display device may further include a touchscreen panel, wherein the insulating coating layer is attached to thetouch screen panel.

In some embodiments, the retardation coating layer may delay the phaseof the transmitted light by a quarter wavelength (λ/4), a firstdirection of an optical axis of the retardation coating layer and asecond direction of an optical axis of the polarizer coating layer mayform an angle of 45°, and the optical axis of the base film may be thesame as the optical axis of the polarizer coating layer.

In some embodiments, the polarizer coating layer may be disposed beneaththe base film, the retardation coating layer may be disposed beneath thepolarizer coating layer, and the anti-reflection film may furtherinclude an adhesive layer disposed beneath the retardation coatinglayer.

In some embodiments, the display device may further include a touchscreen panel, wherein the adhesive layer is attached to the touch screenpanel.

In some embodiments, the retardation coating layer may delay the phaseof the transmitted light by a quarter wavelength (λ/4).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a foldable display device according to an exemplaryembodiment of the inventive concept.

FIG. 2 illustrates the foldable display device of FIG. 1 in a foldedstate.

FIG. 3 is a cross-sectional view of a foldable display device accordingto an exemplary embodiment of the inventive concept.

FIG. 4 is a top plan view of a touch screen panel in a foldable displaydevice according to an exemplary embodiment of the inventive concept.

FIG. 5 is a cross-sectional view of a touch electrode of the touchscreen panel of FIG. 4 (taken along line V-V of FIG. 4).

FIG. 6 is a cross-sectional view of an anti-reflection film according toan exemplary embodiment of the inventive concept.

FIG. 7 is a graph of the retardation values (Rin) of an elastomer (EL)and polyurethane (PU) as a function of wavelength, whereby the elastomer(EL) and polyurethane (PU) may be used as a base film of ananti-reflection film according to an exemplary embodiment of theinventive concept.

FIG. 8 is a graph of the retardation values of a retardation coatinglayer as a function of its thickness according to an exemplaryembodiment of the inventive concept.

FIG. 9 illustrates the directions of the optical axes of a base filmretardation coating layer, and a polarizer coating layer in theanti-reflection film according to an exemplary embodiment of theinventive concept.

FIG. 10 is a graph of the measured transmittance of an anti-reflectionfilm as a function of wavelength according to an exemplary embodiment ofthe inventive concept.

FIG. 11 is a cross-sectional view of an anti-reflection film accordingto another exemplary embodiment of the inventive concept.

FIG. 12 is a cross-section of an anti-reflection film according toanother exemplary embodiment of the inventive concept.

FIG. 13 illustrates the directions of the optical axes of the base film,the retardation coating layer, and the polarizer coating layer in theanti-reflection film of FIG. 12.

FIG. 14 is a cross-sectional view of an anti-reflection film accordingto another exemplary embodiment of the inventive concept.

FIG. 15 is a cross-sectional view of an anti-reflection film accordingto another exemplary embodiment of the inventive concept.

FIG. 16 is a cross-sectional view of an anti-reflection film accordingto another exemplary embodiment of the inventive concept.

FIG. 17 is a cross-sectional view of an anti-reflection film accordingto another exemplary embodiment of the inventive concept.

DETAILED DESCRIPTION

The present inventive concept will be described more fully herein withreference to the accompanying drawings in which exemplary embodimentsare shown. As those skilled in the art would realize, the describedembodiments may be modified in various ways without departing from thespirit or scope of the present disclosure.

In the embodiments, like reference numerals designate like elementshaving the same configuration.

In the drawings, the thicknesses of layers, films, panels, regions,etc., may be exaggerated for clarity. It will be understood that when anelement such as a layer, film, region, or substrate is referred to asbeing “on” another element, it can be directly on the other element, ordisposed on the other element with one or more intervening elementsbeing present. In contrast, when an element is referred to as being“directly on” another element, there are no intervening elementspresent. Likewise, it will be understood that when an element such as alayer, film, region, or substrate is referred to as being “beneath”another element, it can be directly beneath the other element, ordisposed beneath the other element with one or more intervening elementsbeing present.

FIG. 1 illustrates a foldable display device 100 according to anexemplary embodiment of the inventive concept. FIG. 2 illustrates thefoldable display device 100 of FIG. 1 in a folded state.

It should be noted that the appearance of the foldable display device100 may be modified in various ways by one of ordinary skill in the art.

The foldable display device 100 includes a body 180 having a firstportion 181, a second portion 182, and a hinge portion 183 connectingthe first portion 181 and the second portion 182. The center of thehinge portion 183 forms a folding axis H when the foldable displaydevice 100 is folded. An optical film 195 may be attached to an upperportion of a screen of the foldable display device 100 to improve thequality of the displayed image. For example, the optical film 195 mayinclude at least one of a polarization film, an anti-reflection film,and an antiglare film to be attached to the upper portion of the screen.

A panel portion 500 (illustrated in FIG. 3) may be installed inside thebody 180. The panel portion 500 will be described with reference to FIG.3. In the interest of clarity, a description of the first portion 181,second portion 182, and hinge portion 183 of the body 180 of thefoldable display device 100 of FIGS. 1 and 2 shall be omitted from thedescription of FIG. 3.

FIG. 3 is a cross-sectional view of the foldable display device 100according to an exemplary embodiment of the inventive concept.

FIG. 3 illustrates the panel portion 500 when the foldable displaydevice 100 is in an unfolded state. The panel portion 500 includes afirst protective window 101, a display panel 200 disposed on the firstprotective window 101, a touch screen panel 300 disposed on the displaypanel 200, an anti-reflection film 400 disposed on the touch screenpanel 300, and a second protective window 102 disposed on theanti-reflection film 400.

The first protective window 101 and the second protective window 102 maybe formed of a flexible and elastic polymer material. In someembodiments, the polymer material may be transparent. For example, thefirst protective window 101 and the second protective window 102 may beformed of one or more of the following materials: PMMA (polymethylmethacrylate), PDMS (polydimethylsiloxane), transparent silicon resin,and Teflon.

The display panel 200 may include a plurality of display diodes. Theplurality of display diodes may include display diodes based on anorganic light emitting diode (OLED) display, a liquid crystal display(LCD), a field emission display (FED), and/or a plasma display panel(PDP). Accordingly, the display panel 200 may include a display panelfrom any one of the following: an organic light emitting diode display,a liquid crystal display, a field emission display, or a plasma displaypanel.

The display panel 200 and the touch screen panel 300 may be attachedtogether by an adhesive. The touch screen panel 300 and theanti-reflection film 400 may also be attached together by an adhesive.

Next, the touch screen panel 300 of FIG. 3 will be described withreference to FIGS. 4 and 5.

FIG. 4 is a top plan view of the touch screen panel 300 in the foldabledisplay device 100 according to an exemplary embodiment of the inventiveconcept. FIG. 5 is a cross-sectional view of a touch electrode in thetouch screen panel 300 of FIG. 4 (taken along line V-V of FIG. 4).

Referring to FIGS. 4 and 5, the touch screen panel 300 includes atransparent substrate 301, a plurality of driving electrodes 310disposed on the transparent substrate 301 an insulating layer 315disposed on the plurality of driving electrodes 310, and a plurality ofsensing electrodes 320 disposed on the insulating layer 315. Theplurality of driving electrodes 310 and sensing electrodes 320 areconnected to a sensing circuit portion 340 through a sensing wire 330.

The transparent substrate 301 may be formed of a transparent polymercompound (such as PET (polyethylene terephthalate) or PC(polycarbonate)).

The driving electrodes 310 may be disposed in a first direction, and thesensing electrodes 320 may be disposed in a second direction that isperpendicular to the first direction. The driving electrodes 310 and thesensing electrodes 320 may be formed as a metal mesh. The metal mesh maybe manufactured by fine patterning of a metal having high conductivity.

The metal mesh may be manufactured using a printing method, animprinting method, a lithography method, or other similar methods.

The printing method includes forming a transparent electrode (or wire)directly on a substrate using a gravure or offset process. Thetransparent electrode (or wire) may be formed of a transparentconductive material or metal.

The imprinting method includes etching a transparent conductive layer(or metal layer) through a fine pattern to form a transparent electrode(or wire) after the fine pattern has been formed on the transparentconductive layer (or metal layer).

The lithography method includes forming a fine pattern on the substrateusing a light source (such as light of a particular wavelength, a laser,or an electronic beam), and etching a transparent conductive layer (ormetal layer) using the fine pattern to form a transparent electrode (orwire).

The metal mesh may include a plurality of metal patterns, and may beformed of a metal (such as copper (Cu), aluminum (Al), molybdenum (Mo),or silver (Ag)). In some embodiments, the metal patterns may have a linewidth of about 0.1 um to about 10 um. As previously described, thedriving electrodes 310 and the sensing electrodes 320 may be formed asthe metal mesh. Accordingly, the driving electrodes 310 and the sensingelectrodes 320 have high conductivity and transparency.

Referring to FIG. 5, the insulating layer 315 is interposed between thedriving electrodes 310 and the sensing electrodes 320, so as to separatethe driving electrodes 310 from the sensing electrodes 320. Theinsulating layer 315 may be formed of an inorganic insulating material(such as silicon oxide (SiO₂) or silicon nitride (SiNx)). In someembodiments, the insulating layer 315 may be formed of an organicinsulating material (such as a cellulose derivative, an olefin-basedresin, an acryl-based resin, a vinyl chloride-based resin, astyrene-based resin, a polyester-based resin, a polyamide-based resin, apolycarbonate-based resin, a polycycloolefin resin, or an epoxy resin).

Since the driving electrodes 310 and the sensing electrodes 320 areseparated by the insulating layer 315, a capacitance therefore resultsbetween the driving electrodes 310 and the sensing electrodes 320.

The sensing circuit portion 340 may be configured to apply a touchdetection signal to the driving electrodes 310. Also, the sensingcircuit portion 340 may be configured to sense a change in capacitancethrough the sensing electrodes 320 so as to detect a touch position.

Next, the anti-reflection film 400 of FIG. 3 (that is disposed on thetouch screen panel 300) will be described with reference to FIGS. 6 to10.

FIG. 6 is a cross-sectional view of the anti-reflection film 400according to an exemplary embodiment of the inventive concept.

Referring to FIG. 6, the anti-reflection film 400 includes a base film410, a retardation coating layer 420 disposed on the base film 410, apolarizer coating layer 430 disposed on the retardation coating layer420, and an over-coating layer 440 disposed on the polarizer coatinglayer 430.

The base film 410 may serve as a substrate for the anti-reflection film400. As previously mentioned the anti-reflection film 400 is attached tothe touch screen panel 300. The base film 410 may be formed of aflexible material capable of transmitting light. In some embodiments, aretardation effect of the base film 410 may be zero. In someembodiments, an in-plane retardation value (Rin) and a thicknessdirection retardation value (Rth) of the base film 410 may be about 10nm or less.

The base film 410 may be formed of an elastomer (EL). The elastomer (EL)may include a polymer compound having an elastic property. The base film410 may also be formed of polyurethane (PU) (a polymer compound bondedby a urethane bond) or other similar materials. It should be noted thatthe folding functions and flexibility of the foldable display device 100may be improved by forming the base film 410 out of elastomer (EL) orpolyurethane (PU). In some embodiments, the base film 410 may have athickness of about 20 um.

FIG. 7 is a graph of the retardation values (Rin) of an elastomer (EL)and polyurethane (PU) as a function of wavelength. The elastomer (EL)and polyurethane (PU) may be used as a base film of the anti-reflectionfilm 400 according to an exemplary embodiment of the inventive concept.

Referring to FIG. 7, it is observed that the retardation values (Rin) ofthe elastomer (EL) is less than 2 nm when the wavelength is greater than450 nm. Also, the retardation values (Rin) of polyurethane (PU) isapproximately 4 nm or less when the wavelength is greater than 450 nm.Accordingly, the elastomer (EL) and polyurethane (PU) are suitable foruse in the base film 410.

Referring back to FIG. 6, the retardation coating layer 420 is designedto delay a phase of the transmitted light by λ/4. In other words, aphase difference of the retardation coating layer 420 is λ/4. Theretardation coating layer 420 may be formed using a reactive liquidcrystal monomer (e.g. reactive mesogens). Alternatively, in someembodiments, the retardation coating layer 420 may be formed using aphoto-alignment or photo-reactive polymer.

Next, a method of forming the retardation coating layer 420 using areactive liquid crystal monomer will be described.

First, an alignment layer (not illustrated) is formed on the base film410. The alignment layer may be formed of an alignment material (such aspolyimide or polyamide). More particularly, materials such as polyimideor polyamide may be applied on the base film 410, fired, and pressed bya roll in a particular alignment direction, thereby forming thealignment layer.

When the reactive liquid crystal monomers re applied onto the alignmentlayer, the reactive liquid crystal monomers arrange in the alignmentdirection of the alignment layer. Thus, the reactive liquid crystalmonomers will be arranged in a predetermined direction according to thealignment direction.

The reactive liquid crystal monomers include a liquid crystal materialincluding an end group capable of being polymerized. For example, thereactive liquid crystal monomers may include a monomer moleculeincluding a terminal group that is capable of being polymerized withmesogen, and that expresses a liquid crystal property so as to have aliquid crystal phase. Generally, since a liquid crystal has both analignment property of a crystal and the fluidity of a liquid, the liquidcrystal may be uniformly applied onto a substrate having a area witheasy arraying of the liquid crystal molecules. When the reactive liquidcrystal monomers (aligned in a liquid crystal phase) are polymerized, across-linked polymer network may be obtained while maintaining anarrangement phase of the liquid crystal. Calamitic mesogen expressing anematic liquid crystal phase may be used as the mesogen to polarize theterminal group of the monomer molecule. In addition, an acryl group or amethacryl group (that can be subjected to radical polymerization) may beused as the terminal group to be polymerized. One of ordinary skill inthe art would appreciate that any functional group capable of beingpolymerized may be used as the terminal group.

Next, a method of forming the retardation coating layer 420 using aphoto-alignment or photo-reactive polymer will be described.

A liquid crystal polymer, a liquid crystal low molecule, or an oligomerhaving a photo-sensitive group exhibiting optical anisotropy and amesogen-forming group exhibiting a liquid crystal property in apredetermined temperature section according to irradiation of linearlypolarized light, or a mixture thereof, may be used as the photo-reactivepolymer.

The photo-reactive polymer may be formed of a polymethacrylate-basedmain chain with one or more side chains connected to the main chain.Each side chain includes at least one liquid crystal material, and aphoto-reactive material is provided as the terminal group of the sidechain to cause a photo-isomerization reaction or a photo-dimerizationreaction. In some embodiments, a hydrogen bond group may be provided asthe terminal group.

An azobenzene group may be used as the liquid crystal material; and acinnamate group, coumarin group, or benzylidenephthalimidine group maybe used as the photo-reactive material. When the cinnamate group isincluded as a photo-reactive group in the photo-reactive material, ahomopolymer having a liquid crystal group and the photo-reactive groupformed of cinnamate may be bonded as a side chain to a main chain formedof polymethacrylate. The homopolymer including the cinnamate group andexhibiting the liquid crystal property through the hydrogen bond withthe adjacent side chain may be bonded to the main chain formed ofpolymethacrylate. In some embodiments, a heteropolymer or a copolymerhaving the cinnamate group and the liquid crystal group and anadditional liquid crystal group may be simultaneously bonded to a mainchain formed of polymethacrylate.

The photo-reactive polymer may have a refractive anisotropy (dn) ofabout 0.08 to 0.20, and the retardation value of the retardation coatinglayer 420 may be adjusted by varying the thickness of the photo-reactivepolymer.

When linearly polarized light is irradiated on the photo-reactivepolymer, photo-isomerization and photo-dimerization reactions may occurin the photo-reactive polymer so as to cause anisotropy in thephoto-reactive polymer. The optical anisotropy may be increased byheat-treating the photo-reactive polymer to arrange the photo-reactivepolymer in a predetermined direction.

The photo-reactive polymer may be applied on the base film 410 and bakedat a temperature of about 30 to 80° C. Linearly polarized light (such asultraviolet rays) may be irradiated on the applied photo-reactivepolymer, and the photo-reactive polymer is then fired at a temperatureof 80 to 150° C. for about 10 minutes to form the retardation coatinglayer 420. Since a direction of an optical axis of the retardationcoating layer 420 is perpendicular to a polarization direction of theultraviolet rays, the direction of the optical axis of the retardationcoating layer 420 may be modified by adjusting the polarizationdirection of the ultraviolet rays.

In some embodiments, the retardation coating layer 420 may be formedusing a polyvinyl alcohol (PVA) coating method.

FIG. 8 is a graph of the retardation values of a retardation coatinglayer 420 as a function of its thickness according to an exemplaryembodiment of the inventive concept. The retardation coating layer 420includes a reactive liquid crystal monomer having a refractiveanisotropy (dn) of 0.10 to 0.12. It can be observed from FIG. 8 that theretardation value increases with the thickness of the retardationcoating layer 420.

The thickness of the retardation coating layer 420 may be set to about 1to 2 um, so as to delay light transmitted through the retardationcoating layer 420 by λ/4. For example, if the refractive anisotropy ofthe reactive liquid crystal monomer is 0.1 and the wavelength of lighttransmitted through the retardation coating layer 420 is 550 nm (whichis an intermediate wavelength of a visible light region), theretardation value of light transmitted through the retardation coatinglayer 420 becomes 137.5 nm. The thickness of the retardation coatinglayer 420 corresponding thereto will then be about 1 to 2 um.Accordingly, the phase of light in the visible light region may bedelayed by λ/4 where passing through the retardation coating layer 420having a thickness of about 1 to 2 um.

Referring back to FIG. 6, the polarizer coating layer 430 transformsexternal light into linearly polarized light having a polarizationcomponent in a predetermined direction. Accordingly, the polarizationcomponent in the predetermined direction may be transmitted through thepolarizer coating layer 430.

The polarizer coating layer 430 may be formed as a lyotropic type or ahost-guest type.

For example, a liquid crystal including a lyotropic polymer may beapplied on the fired retardation coating layer 420, and the lyotropicpolymer may be arranged in a row using photo-alignment and then fired toform a lyotropic polarizer coating layer 430.

When a liquid crystal (a host) and a dichroic dye (a guest) are mixed,the host may be arranged in the alignment direction of a lower alignmentlayer (not illustrated) together with the guest (dichroic dye) and thenfired to form a host-guest type polarizer coating layer 430. In thiscase, the lower alignment layer may be applied on the fired retardationcoating layer 420 and fired, and the fired alignment layer may bepressed by a roll to form the lower alignment layer in the alignmentdirection. A perylene-based dye may be used as the dichroic dye. Asmectic liquid crystal having a two-dimensional regular arrangement maybe used as the liquid crystal. The smectic liquid crystal is a highlyrefractive liquid crystal (as compared to a nematic liquid crystal whichhas a predetermined arrangement in one dimension).

The over-coating layer 440 serves to protect the retardation coatinglayer 420 and the polarizer coating layer 430. An over-coatingcomposition may be applied on the polarizer coating layer 430 and thenbaked to form the over-layer 440. Acryl-based and silicon-based oxidelayers (or other similar materials) may be used as the over-coatinglayer 440. A UV (ultraviolet)-absorber capable of absorbing light of anultraviolet ray region may be added to the over-coating layer 440.Examples of the UV-absorber include hydroxyphenyl-benztriazole,hydroxyphenyl-benzophenone, oxalic acid amide, triazine, oxalanilide,cyanoacrylate, salicylic acid, hydroxyphenylpyrimidine, or other similarmaterials. The over-coating layer 440 may be formed having a thicknessof about 1 um.

FIG. 9 illustrates the directions of the optical axes of the base film410, the retardation coating layer 420, and the polarizer coating layer430 in the anti-reflection film 400 according to an exemplary embodimentof the inventive concept.

Referring to FIG. 9, an arrow is illustrated in each of the base film410, the retardation coating layer 420, and the polarizer coating layer430. Each arrow represents a direction of the optical axis. Asillustrated in FIG. 9, the directions of the optical axes of theretardation coating layer 420 and the polarizer coating layer 430 forman angle of 45°. Since the retardation value of the base film 410 is 10nm or less, the retardation value does not affect an opticalcharacteristic of the base film 410. However, to minimize a change inoptical characteristic during the manufacture of the touch screen panel300 (or during folding of the touch screen panel 300), the direction ofthe optical axis of the base film 410 may be the same as the directionof the retardation coating layer 420.

In the anti-reflection film 400 described above the phase of light thatis incident from below the retardation coating layer 420 is delayed byλ/4 after passing through the retardation coating layer 420. The lightis then transformed into linearly polarized light after passing throughthe polarizer coating layer 430, and the linearly polarized light istransmitted through the anti-reflection film 400. Conversely, light thatis incident from above the anti-reflection film 400 transforms intolinearly polarized light having only the polarization component in thepredetermined direction while being transmitted through the polarizercoating layer 430.

For the case in which the light is incident from above theanti-reflection film 400, the polarization direction of the linearlypolarized light is parallel to the polarization direction of thepolarizer coating layer 430. The linearly polarized light is transformedinto circularly polarized light while passing through the retardationcoating layer 420. Thereafter, the circularly polarized light isreflected on the touch screen panel 300 or the display panel 200disposed beneath the anti-reflection film 400, and subsequently thepolarization direction of the circularly polarized light is inverted.For example, left circular polarization is changed into right circularpolarization, and right circular polarization is changed into leftcircular polarization. Circularly polarized light having the changedpolarization direction is transformed into linearly polarized lightafter passing through the retardation coating layer 420 a second time,and the polarization direction of the linearly polarized light isperpendicular to the previous polarization direction (when the lightfirst passed through the polarizer coating layer 430 at an initialstage). Accordingly, the linearly polarized light (that is transformedwhile passing through the retardation coating layer 420 a second time)does not pass through the polarizer coating layer 430 but is insteadabsorbed in the polarizer coating layer 430.

Accordingly, light that is incident on the anti-reflection film 400 fromthe outside is not emitted through the anti-reflection film 400, butlight that is incident on the anti-reflection film 400 from the displaypanel 200 beneath the anti-reflection film 400 may pass through theanti-reflection film 400. Accordingly, a viewer can observe a clearimage (since an external light component is removed).

Next, the differences between a conventional anti-reflection film andthe exemplary anti-reflection film 400 will be described.

A conventional anti-reflection film may be formed by attaching aretardation film (formed of elongating polycarbonate (PC)) and apolarization film (having polyvinyl alcohol (PVA) as a main component)together using an adhesive, and disposing a protective film (formed oftriacetylcellulose (TAC)) on the polarization film. In the conventionalanti-reflection film the thickness of the retardation film is about 56um the thickness of the polarization film is about 12 um, the thicknessof the adhesive is about 10 um, and the thickness of the protective filmis 25 um. Accordingly, the total thickness of the conventionalanti-reflection film may be about 97 um.

In contrast to the conventional anti-reflection film, the totalthickness of the anti-reflection film 400 may be about 26 um or less.This is because the anti-reflection film 400 has a thickness that isabout ¼ the thickness of the conventional anti-reflection film. As aresult, a foldable display device including the anti-reflection film 400may have a reduced bending radius and better bendability compared to aconventional foldable display device.

FIG. 10 is a graph of the measured transmittance of light through theanti-reflection film 400 as a function of wavelength.

Referring to FIG. 10, it is observed that there is no significantdifference between the transmittance of a conventional anti-reflectionfilm and the transmittance of the anti-reflection film 400 when thewavelength is less than about 680 nm.

In the anti-reflection film 400, the transmittance of light in thewavelength region of 400 to 480 nm is slightly higher because theUV-absorber is not added to the over-coating layer 440. If theUV-absorber is added to the over-coating layer 440, the transmittance oflight in the wavelength region of 400 to 480 nm may be reduced. Hightransmittance of light having a wavelength of 680 nm or greater iscaused by a reduction in dichroic ratio of the dichroic dye in thepolarizer coating layer 430. The transmittance may be compensated byadjusting the dichroic ratio of the dichroic dye in the correspondingwavelength region.

Next, different embodiments of the anti-reflection film 400 will bedescribed with reference to FIGS. 11 to 17. In the interest of clarity,the description will focus on the differences between the embodiments inFIGS. 11 to 17 and the embodiment in FIG. 6.

FIG. 11 is a cross-sectional view of an anti-reflection film 400according to another exemplary embodiment of the inventive concept.

Referring to FIG. 11 the anti-reflection film 400 includes a base film410, a retardation coating layer 420 disposed on the base film 410, asecond over-coating layer 450 disposed on the retardation coating layer420, a polarizer coating layer 430 disposed on the second over-coatinglayer 450, and a first over-coating layer 440 disposed on the polarizercoating layer 430.

In contrast to FIG. 6, the embodiment in FIG. 11 includes the secondover-coating layer 450 disposed between the retardation coating layer420 and the polarizer coating layer 430. An over-coating composition maybe applied on the retardation coating layer 420 and then baked to formthe second over-coating layer 450. The second over-coating layer 450protects a liquid crystal layer of the retardation coating layer 420(that is formed using a reactive liquid crystal monomer or aphoto-reactive polymer). The second over-coating layer 450 may be formedhaving a thickness of about 1 um.

It is noted that the reliability and processability of the retardationcoating layer 420 may be improved by disposing the second over-coatinglayer 450 on the retardation coating layer 420.

FIG. 12 is a cross-sectional view of an anti-reflection film 400according to another exemplary embodiment of the inventive concept.

Referring to FIG. 12, the anti-reflection film 400 includes a base film410, a polarizer coating layer 430 disposed on the base film 410, anover-coating layer 440 disposed on the polarizer coating layer 430, aretardation coating layer 420 disposed beneath the base film 410, and aninsulating coating layer 460 disposed beneath the retardation coatinglayer 420.

In contrast to FIG. 6 the polarizer coating layer 430 in FIG. 12 isdisposed on one side of the base film 410, the retardation coating layer420 is disposed on the other side of the base film 410, and theretardation coating layer 420 is disposed between the insulating coatinglayer 460 and the base film 410. The over-coating layer 440 is disposedon the polarizer coating layer 430 on one side of the base film 410. Theinsulating coating layer 460 is disposed on the retardation coatinglayer 420 on the other side of the base film 410.

The insulating coating layer 460 may be formed of polyimide. Theinsulating coating layer 460 may be attached to a touch screen panel300. Alternatively, the insulating coating layer 460 may be removed whenthe anti-reflection film 400 and the touch screen panel 300 adhere toeach other.

The physical properties and an alignment angle of the retardationcoating layer 420 may be changed by irradiating light during the formingof the polarizer coating layer 430. The changes in the physicalproperties and the alignment angle of the retardation coating layer 420depend on the type of liquid crystal material used in the retardationcoating layer 420. Nevertheless, changes in the physical properties andthe alignment angle of the retardation coating layer 420 may beprevented by disposing the retardation coating layer 420 on a side thatis different from (opposite to) the side where the polarizer coatinglayer 430 is disposed.

FIG. 13 illustrates the directions of the optical axes of the base film,the retardation coating layer, and the polarizer coating layer in theanti-reflection film of FIG. 12.

Referring to FIG. 13, when the polarizer coating layer 430 is disposedon the base film 410 and the retardation coating layer 420 is disposedbeneath the base film 410 (as in FIG. 12), the directions of the opticalaxes of the polarizer coating layer 430 and the retardation coatinglayer 420 may form an angle of 45°, and the direction of the opticalaxis of the base film 410 may be the same as the direction of thepolarizer coating layer 430.

Since a retardation value of the base film 410 is 10 nm or less, theretardation value does not affect an optical characteristic of the basefilm 410. However, the direction of the optical axis of the base film410 may be the same as the direction of the polarizer coating layer 430,so as to minimize a change in the optical characteristic during themanufacture of the touch screen panel 300 (or during folding of thetouch screen panel 300).

FIG. 14 is a cross-sectional view of an anti-reflection film 400according to another exemplary embodiment of the inventive concept.

Referring to FIG. 14, the anti-reflection film 400 includes a base film410, a retardation coating layer 420 disposed on the base film 410, apolarizer coating layer 430 disposed on the retardation coating layer420, and an over-coating layer 440 disposed on the polarizer coatinglayer 430. Particles 441 for antiglare, as well as a UV-absorber, may beadded to the over-coating layer 440. Silica (or other similar materials)may be used as the particles 441 for antiglare. Thus, an antiglarefunction may be added to the over-coating layer 440 to adjust a haze,surface roughness, etc.

FIG. 15 is a cross-sectional view of an anti-reflection film 400according to another exemplary embodiment of the inventive concept.

Referring to FIG. 15, the anti-reflection film 400 includes a base film410, a retardation coating layer 420 disposed on the base film 410, apolarizer coating layer 430 disposed on the retardation coating layer420, and an optical coating layer 470 disposed on the polarizer coatinglayer 430. The optical coating layer 470 may include at least one of alow reflectance coating, an anti-reflection coating, and ananti-fingerprint coating. A UV-absorber may be added to the opticalcoating layer 470. The low reflectance coating, the anti-reflectioncoating, and the anti-fingerprint coating may be formed using methodsknown to one of ordinary skill in the art, and a detailed descriptionthereof will be omitted.

FIG. 16 is a cross-sectional view of an anti-reflection film 400according to another exemplary embodiment of the inventive concept.

Referring to FIG. 16, the anti-reflection film 400 includes a base film410, a polarizer coating layer 430 disposed beneath the base film 410, aretardation coating layer 420 disposed beneath the polarizer coatinglayer 430, and an adhesive layer 480 disposed beneath the retardationcoating layer 420. The anti-reflection film 400 is attached to a touchscreen panel 300 by the adhesive layer 480.

The anti-reflection film 400 may be manufactured by forming thepolarizer coating layer 430 on the base film 410, forming theretardation coating layer 420 on the polarizer coating layer 430, andforming the adhesive layer 480 on the retardation coating layer 420. Themethod of forming the polarizer coating layer 430 and the retardationcoating layer 420 is similar to the embodiment previously described inFIG. 6. The adhesive layer 480 may be formed by applying an adhesivematerial on the retardation coating layer 420.

The anti-reflection film 400 may be attached to the touch screen panel300 with the adhesive layer 480 disposed between the touch screen panel300 and the anti-reflection film 400.

Accordingly, after assembly, the touch screen panel 300 is disposed on adisplay panel 200, the adhesive layer 480 is disposed on the touchscreen panel 300, the retardation coating layer 420 is disposed on theadhesive layer 480, the polarizer coating layer 430 is disposed on theretardation coating layer 420, and the base film 410 is disposed on thepolarizer coating layer 430.

FIG. 17 is a cross-sectional view of an anti-reflection film 400according to another exemplary embodiment of the inventive concept.

Referring to FIG. 17, the anti-reflection film 400 includes a base film410, a first retardation coating layer 420 disposed on the base film 410a second over-coating layer 450 disposed on the first retardationcoating layer 420, a second retardation coating layer 490 disposed onthe second over-coating layer 450, a polarizer coating layer 430disposed on the second retardation coating layer 490, and a firstover-coating layer 440 disposed on the polarizer coating layer 430.

The first retardation coating layer 420 delays a phase of incident lightby λ/4, and the second retardation coating layer 490 delays the phase ofincident light by λ/2. The method of forming the first retardationcoating layer 420 is similar to the embodiment previously described inFIG. 6. For example, the second retardation coating layer 490 may beformed using the same method for forming the first retardation coatinglayer 420. An axis of a sum of vectors of the direction of an opticalaxis of the first retardation coating layer 420 and the direction of theoptical axis of the second retardation coating layer 490 has an angle of45° to the direction of the optical axis of the polarizer coating layer430. For example, the direction of the optical axis of the polarizercoating layer 430 may have an angle of 45°, the direction of the opticalaxis of the first retardation coating layer 420 may have an angle of120°, and the direction of the optical axis of the second retardationcoating layer 490 may have an angle of 60°.

The anti-refection film 400 (including the first retardation coatinglayer 420 and the second retardation coating layer 490) allows lightthat is incident from under the anti-reflection film 400 to betransmitted through, and blocks light that is incident from above theanti-reflection film 400. As a result, the light that is incident fromabove the anti-reflection film 400 is reflected. Accordingly, the secondretardation coating layer 490 may expand a bandwidth of the transmittedlight. That is, in the case where only the first retardation coatinglayer 420 is formed, light having a predetermined wavelength istransmitted through the anti-reflection reflection film 400. Incontrast, the anti-reflection film 400 including the first retardationcoating layer 420 and the second retardation coating layer 490 may allowlight having a wider wavelength to be transmitted therethrough.

While this inventive concept has been described in connection with whatis presently considered to be practical exemplary embodiments, it is tobe understood that the inventive concept is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements within the spirit and scope ofthe present disclosure.

What is claimed is:
 1. A display device comprising: an anti-reflectionfilm, wherein the anti-reflection film includes: a base film; apolarizer coating layer disposed beneath the base film and configured topass through a component of light polarized in a specific direction; aretardation coating layer disposed beneath the polarizer coating layerand configured to delay a phase of transmitted light; and an adhesivelayer disposed beneath the retardation coating layer, wherein theretardation coating layer and the polarizer coating layer are formed byapplying a liquid crystal on the base film, and wherein the base film isformed of a flexible material selected from a group consisting of anelastomer and polyurethane.
 2. The display device of claim 1, furthercomprising: a touch screen panel, wherein the adhesive layer is attachedto the touch screen panel.
 3. The display device of claim 1, wherein:the retardation coating layer delays the phase of the transmitted lightby a quarter wavelength (λ/4).
 4. The display device of claim 1,wherein: the base film has an in-plane retardation value (Rin) of 4 nmor less when a wavelength of the transmitted light is greater than 450nm, and the base film has a thickness-direction retardation value (Rth)of 10 nm or less.
 5. A display device comprising: a display panel; anadhesive layer disposed on the display panel; a retardation coatinglayer disposed on the adhesive layer and configured to delay a phase oftransmitted light; a polarizer coating layer disposed on the retardationcoating layer and configured to pass through a component of lightpolarized in a specific direction; and a base film disposed on thepolarizer coating layer and formed of a flexible material selected froma group consisting of an elastomer and polyurethane.
 6. The displaydevice of claim 5, wherein: the retardation coating layer and thepolarizer coating layer are formed by applying a liquid crystal on thebase film.
 7. The display device of claim 5, further comprising: a touchscreen panel disposed on the display panel, wherein the adhesive layeris attached to the touch screen panel.
 8. The display device of claim 5,wherein: the retardation coating layer delays the phase of thetransmitted light by a quarter wavelength (λ/4).
 9. The display deviceof claim 5, wherein: the base film has an in-plane retardation value(Rin) of 4 nm or less when a wavelength of the transmitted light isgreater than 450 nm, and the base film has a thickness-directionretardation value (Rth) of 10 nm or less.